Radio receiving apparatus



.Nov. 18, 1941. B. s. VILKOM ERSON Q 2,262,979

I RADIO RECEIVING APPARATUS Filed May 29, 1941 2 Sheets-Sheet l Nov. 18, 1941. B. s. VILKOMERSON 2,262,979

RADIO RECEIVING APPARATUS Patented Nov. 18, 1941 UNITED STATES PATE T" OFFICEA, A

RADIO RECEIVING APPARATUS Benjamin S. Vilkomerson, Newton, Mass., as-

signor to David Housman and Abraham J. Housman, Winthrop, Mass.

Application May 29, 1941, Serial No. 395,729

8 Claims.

. The present, invention relates. to radio receiving apparatus and, more particularly to radio sets 01? the portable type with built-in loop antennas.

As is well known, the effectiveness of a loop antenna, depends upon its area and the figure of merit (Q) thereof, and the number of turns therein. It has been proposed, therefore, to wind a loop antenna on the outside of a radio receiving set and to compensate for the damping of the received oscillations due to the proximity of metallic elements within the loop. by amplifying the current in the input circuit of the first tube by transferring thereto energy from the output circuit by a coil in the plate circuit that is adjustable in position with the loop antenna. The proper adjustment of the movable coil with respect to the loop antenna being somewhat critical, such receivers have not come into general use, and, furthermore, an adjustable coil protruding from the cabinet would be impracticable in portable midget sets where size is a dominant factor.

The object of the present invention is the provision of a set having a fixed coil wound on the outer surface of the cabinet in the form of serially connected turns, each turn passing around such sides in a substantially vertical plane, one portion of the coil being a loop antenna and the other portion, a feed-back coil connected to the output circuitof the first tube of the receiver.

, The relation of the parts may be such that maximum regeneration is obtained at the high frequency end of the band for which the receiver is designed, or by including a fixed capacitance having appreciable reactance to the lower frequencies of said band in the lead from the common terminal of the loop antenna and feed-back coil to the cathode of said tube, maximum amplification may be obtained at the low frequency end of said band. By properlyproportioning the parts, the regeneration may be made substantially equal for all frequencies within the range for which the receiver is designed.

The fixed coil may be located inside the casing and the coupling of the input and output circuits effected by either of the means above set forth, or by both of them. v

Another object is the provision of means whereby the plate feed-back is augmented by feedback from the screen grid. This is particularly desirable in very small portable sets where a portion of the loop antenna is necessarily in closer proximity to the chassis than in portable sets having larger cabinets. This embodiment of my invention is not limited to use with a loop antenna, which, of course, is an inductance, as any other form of inductance in the input circuit of the tube input circuit may be used with either a loop antenna or an antenna of any other type.

Other objects of my invention and the means for effecting them will hereinafter appear.

In the drawings accompanying and forming a part of this specification,

Figure 1 is a diagram of a portion of a superheterodyne receiving system embodying my invention.

Fig. 2 is a. perspective and somewhat diagrammatic view of one form of cabinet that may be employed in my improved receiving apparatus; and

" Fig. 3 is-an end view thereof,

Fig. 4 is a diagram of a circuit whereby screen grid feed-back is obtained. I

In the particular drawings selected for more fully disclosing the underlying principle of my invention, [0 is a mixing tube, for example, one of the 1R5 type, the plate I I of which is connected to the primary of the intermediate frequency circuit l2, and the latter is connected by the lead l3 that may include the blocking condenser M to one terminal I5 of the feed-back coil [6 which, in turn, is connected at I1. to one end of the loop antenna [8, the other end I!) of which goes to the control grid of the mixing tube. The feed-back coil I6 and loop antenna I8 constitute a fixed coil 20, the convolutions of which are disposed on the outer surface of the cabinet in the form of serially connected turns each passing around four sides of the cabinet in a substantially vertical plane, one portion of the coil constituting a loop antenna and the other portion a feed-back circuit. Preferably, as shown in Fig. 3, the wires of said coil are disposed in grooves 2| formed in the sides of the cabinets and it is desirable that they should be bunched together at or near either the forward or the rearward portion of the boxes in order to reduce damping, as indicated in Fig. 3 diagrammatically.

The B battery is connected by the resistor R between ground and the output circuit of the tube. V

In the lead between the terminal [1 and the cathode 22 is included a condenser 23, and be-- tween said condenser and the common terminal between the feed-back coil and loop antenna is connected one terminal of the automatic volume control circuit.

When maximum amplification at the high frequency end of the bandis desired, the condenser 23. may be of relatively large capacitance and cure by Letters Patent is:

providing, of course, that the capacitance 23has appreciable reactance at the lower frequencies of the band for which the receiver is designed.

Fig. 4 shows a circuit arrangement whereby V V the plate feed-back is augmented by feed-back from the screen grid IlJb. In this circuit the fixed loop antenna l8 wound and disposed as aforesaid, is inductively related to the feed-back coil 24 which is wound and disposed in the same way as feed-back coil I5 of Fig 1 which is inductively related to the loop antenna 18 and c nductively connected thereto at the point H, but in Fig. 4 the feed-back coil 24 is not conductively connected to the loopantenna. The terminal IQ of the loop antenna is connected to the signal grid Illa and the other terminal thereof isconnected to the cathode 22 inthe manner indicated, viz., through the chassis (not shown) by the grounds G, G, indicating connections to the chassis, or in any other suitable manner. By the conductor 25 the screen grid [0b is connected to one terminal of the coil 24 and the other is connected by the lead 26 to the primary 2! of the oscillator 28, said primary gOing to B+. The oscillator is of course connected to the oscillator grid lllc. It. hasbeen found that when the connections are made in the manner indicated, the

capacitive feed-back from the plate and the inductive feed-back from the screen grid are cumulative andthat the excessive damping due to the extremely close proximity of the loop antenna to the chassis and other metallic elements within the cabinet is compensated for. As in the case of the system shown in Fig.1, it is not essential that the antenna and feedback coil be disposed on the outside of the cabinet in the case of sets of the larger type, either portable or fixed.

I Having thus described an illustrative embodiment of my invention without, however, limiting the same thereto, what I claim and desire to se- 1, A radio receiving apparatus comprising in combination, a cabinet, a fixed coil, the convolutions of which are disposed on the outer surface of said cabinet in the formof serially connected turns each passing around four sides of said cabinet in a substantially. vertical plane, one

. portion of said coil constituting a loop antenna and the other portion a feed-back coil, a receiving circuit disposed within said cabinet, an electron discharge device in said receiving circuit, said electrondischarge device comprising a grid, a plate and a cathode, means connecting-one terminal of said loop antenna to said grid, a conductor connecting said plate to one terminal of said feed-back coil and a lead connecting said cathode to the'terminal common to said feed back coil and said loop antenna.

2. A radio receiving apparatus comp rising'in combination, a cabinet, a fixed loop antenna,'the

convolutions of which are disposed on theouter surface of said cabinet in the, form of serially connected turns each passing around four sides of said cabinet in a substantially vertical plane, a receiving circuit disposed within said cabinet,

an electron discharge device in said receiving,

circuit, said electron discharge device comprising a grid, a plate and a cathode, means connecting one terminal of said loop antenna to said grid, a lead connecting the other terminal of said loop antenna to said cathode, said lead including a fixed capacitance having appreciable reactance to the lower frequencies of the band for which the receiver is designed, and a conductor from .said plate tosaid loop antenna.

disposed within said cabinet, an electron discharge device in said receiving circuit, said electron discharge device comprising a grid, a

plate and a cathode, means connecting one termi-' nal of said loop antenna to said grid, a conductor connecting said plate to one terminal of said feed-back coil, and a lead connecting said cathode to the terminal common to' said feed-back coil and said loop antenna, said lead including a fixed capacitance having appreciable reactance to the lower frequencies of the band for which the receiver is designed.

4. A radio receiving apparatus comprising in combination, a fixed coil having serially-connected convolutions each lying in a substantially vertical plane, one portion of said coil constituting a loop antenna and the other portion of feed-back coil, a receiving circuit, an electron discharge device in said receiving circuit;

' conductor connecting said plate to one terminal of said feed-back coil, and ,a lead connecting said cathode to the terminal common to said feedback coil and said loopantenna, said lead including a fixed capacitance having appreciable reactance to the lower frequencies of the band,

for which the receiver is designed.

' 5. A radio receiving apparatus comprising in combination, a cabinet, a fixed loop antenna, the

convolutions of which are disposed on the outer surface of said cabinet in the form of serially connected turns each passing around four sides of said cabinet in a substantially vertical plane, a'

fixed feed-back coil in inductive relation to said loop antenna, said feed-back coil being disposed on the outer surface of said cabinet in a substantially vertical plane, a receiving circuit dis posed within said cabinet, an electron discharge device in said receiving circuit, said electron discharge device comprising a signal grid, ascreen grid, a plate and acathode, 'means connecting plate to said loop antenna, and a conductor from said screen grid to said feed-back coil.

6. A radio receiving apparatus comprising in; combination a cabinet, a'fixed loop antenna, the t convolutions of which are disposed on the outer surface of said cabinet in the form of serially connected turns each passing around four sides of said cabinet in a substantially vertical plane, a fixed feed-back coil in inductive relation to said loop antenna, said feed-back coil being disposed on the outer surface of said cabinet in a substantially vertical plane, a receiving circuit disposed within said cabinet, an electron discharge device in said receiving circuit, said electron discharge device comprising a signal grid, a screen grid, a plate and a cathode, means connecting one terminal of said loop antenna to said signal grid, a lead connecting the other terminal of said loop antenna to said cathode, a conductor from said plate to said loop antenna, and a conductor from said screen grid to said feed-back coil.

'7. A radio receiving apparatus comprising in combination a cabinet, a fixed loop antenna having serially connected convolutions each lying in a substantially vertical plane, a fixed feed-back coil in inductive relation to said loop antenna, said feed-back coil being disposed in a substantially vertical plane, a receiving circuit disposed within said cabinet, an electron discharge device in said receiving circuit, said electron discharge device comprising a signal grid, a screen grid, a

plate and a cathode, means connecting one terminal of said loop antenna to said signal grid, a lead connecting the other terminal of said loop antenna to said cathode, said lead including a fixed capacitance having appreciable reactance to the lower frequencies of the band for which the receiver is designed, a conductor from said plate to said loop antenna, and a conductor from said screen grid to said feed-back coil.

8. A radio receiving apparatus comprising in combination a cabinet, a fixed loop antenna having serially connected convolutions each lying in a substantially vertical plane, a fixed feed-back coil in inductive relation to said loop antenna, said feed-back coil being disposed in a substantially vertical plane, a receiving circuit disposed within said cabinet, an electron discharge device in said receiving circuit, said electron discharge device comprising a signal grid, a screen grid, a plate and a cathode, means connecting one terminal of said loop antenna to said signal grid, a lead connecting the other terminal of said ,loop antenna to said cathode, a conductor from said plate to said loop antenna, and a conductor from said screen grid to said feed-back coil.

BENJAMIN S. VILKOMERSON. 

